Daniel Shikanai Kerr

Ric-8B interacts with Gαolf and Gγ13 and co-localizes with Gαolf, Gβ1 and Gγ13 in the cilia of olfactory sensory neurons

Olfactory sensory neurons are able to detect odorants with high sensitivity and specificity. We have demonstrated that Ric-8B, a guanine nucleotide exchange factor (GEF), interacts with Galphaolf and enhances odorant receptor signaling. Here we show that Ric-8B also interacts with Ggamma13, a divergent member of the Ggamma subunit family which has been implicated in taste signal transduction, and is abundantly expressed in the cilia of olfactory sensory neurons. We show that Gbeta1 is the predominant Gbeta subunit expressed in the olfactory sensory neurons. Ric-8B and Gbeta1, like Galphaolf and Ggamma13, are enriched in the cilia of olfactory sensory neurons. We also show that Ric-8B interacts with Galphaolf in a nucleotide dependent manner, consistent with the role as a GEF. Our results constitute the first example of a GEF protein that interacts with two different olfactory G protein subunits and further implicate Ric-8B as a regulator of odorant signal transduction.

Aging Effects on Whole-Brain Functional Connectivity in Adults Free of Cognitive and Psychiatric Disorders

Aging is associated with decreased resting-state functional connectivity (RSFC) within the default mode network (DMN), but most functional imaging studies have restricted the analysis to specific brain regions or networks, a strategy not appropriate to describe system-wide changes. Moreover, few investigations have employed operational psychiatric interviewing procedures to select participants; this is an important limitation since mental disorders are prevalent and underdiagnosed and can be associated with RSFC abnormalities. In this study, resting-state fMRI was acquired from 59 adults free of cognitive and psychiatric disorders according to standardized criteria and based on extensive neuropsychological and clinical assessments. We tested for associations between age and whole-brain RSFC using Partial Least Squares, a multivariate technique. We found that normal aging is not only characterized by decreased RSFC within the DMN but also by ubiquitous increases in internetwork positive correlations and focal internetwork losses of anticorrelations (involving mainly connections between the DMN and the attentional networks). Our results reinforce the notion that the aging brain undergoes a dedifferentiation processes with loss of functional diversity. These findings advance the characterization of healthy aging effects on RSFC and highlight the importance of adopting a broad, system-wide perspective to analyze brain connectivity.

Physical exercise improves peripheral BDNF levels and cognitive functions in mild cognitive impairment elderly with different bdnf Val66Met genotypes.

The benefits of physical exercise on improvements in brain-derived neurotrophic factor (BDNF) levels and cognitive functioning have been reported in the literature. However, the variability of individual responses may be linked to genetic differences. BDNF is considered one of the most plausible factors involved in the cognitive benefits associated with physical activity practice. A single nucleotide polymorphism localized in the gene that codes BDNF results in a missense mutation that promotes an amino acid substitution (Val66Met) in the protein. This process has been associated with decreased levels of BDNF secretion, with corresponding impairments in specific cognitive functions. Therefore, the objective of this study was to analyze the effects of a multimodal physical exercise program on peripheral BDNF levels and cognitive functions in elderly individuals with mild cognitive impairment (MCI). The participants were genotyped for the BDNF Val66Met polymorphism. Cognitive functions were assessed by the Montreal Cognitive Assessment (MoCA) prior to and after the intervention. Forty-five participants were assigned to the control and trained groups. The trained group participated in a multimodal physical training for a 16-week period. The results showed a significant between-subjects interaction (p < 0.05), which indicates the beneficial contribution of training on cognitive functions independent of the BDNF genotype. However, only participants with BDNF-Met genotypes exhibited significant improvements in peripheral BDNF levels. The BDNF genotype appears to modulate the effects of physical exercise on BDNF secretion, but it does not influence cognition. This is the first study that evaluated the influence of a BDNF polymorphism on physical activity and cognition performance in elderly MCI individuals.

Ric-8A, a Gα Protein Guanine Nucleotide Exchange Factor Potentiates Taste Receptor Signaling

Taste receptors for sweet, bitter and umami tastants are G-protein-coupled receptors (GPCRs). While much effort has been devoted to understanding G-protein-receptor interactions and identifying the components of the signalling cascade downstream of these receptors, at the level of the G-protein the modulation of receptor signal transduction remains relatively unexplored. In this regard a taste-specific regulator of G-protein signaling (RGS), RGS21, has recently been identified. To study whether guanine nucleotide exchange factors (GEFs) are involved in the transduction of the signal downstream of the taste GPCRs we investigated the expression of Ric-8A and Ric-8B in mouse taste cells and their interaction with G-protein subunits found in taste buds. Mammalian Ric-8 proteins were initially identified as potent GEFs for a range of Gα subunits and Ric-8B has recently been shown to amplify olfactory signal transduction. We find that both Ric-8A and Ric-8B are expressed in a large portion of taste bud cells and that most of these cells contain IP3R-3 a marker for sweet, umami and bitter taste receptor cells. Ric-8A interacts with Gα-gustducin and Gαi2 through which it amplifies the signal transduction of hTas2R16, a receptor for bitter compounds. Overall, these findings are consistent with a role for Ric-8 in mammalian taste signal transduction.

Long-Term Lithium Treatment Increases cPLA2 and iPLA2 Activity in Cultured Cortical and Hippocampal Neurons

Background: Experimental evidence supports the neuroprotective properties of lithium, with implications for the treatment and prevention of dementia and other neurodegenerative disorders. Lithium modulates critical intracellular pathways related to neurotrophic support, inflammatory response, autophagy and apoptosis. There is additional evidence indicating that lithium may also affect membrane homeostasis. Objective: To investigate the effect of lithium on cytosolic phospholipase A2 (PLA2) activity, a key player on membrane phospholipid turnover which has been found to be reduced in blood and brain tissue of patients with Alzheimer’s disease (AD). Methods: Primary cultures of cortical and hippocampal neurons were treated for 7 days with different concentrations of lithium chloride (0.02 mM, 0.2 mM and 2 mM). A radio-enzymatic assay was used to determine the total activity of PLA2 and two PLA2 subtypes: cytosolic calcium-dependent (cPLA2); and calcium-independent (iPLA2). Results: cPLA2 activity increased by 82% (0.02 mM; p = 0.05) and 26% (0.2 mM; p = 0.04) in cortical neurons and by 61% (0.2 mM; p = 0.03) and 57% (2 mM; p = 0.04) in hippocampal neurons. iPLA2 activity was increased by 7% (0.2 mM; p = 0.04) and 13% (2 mM; p = 0.05) in cortical neurons and by 141% (0.02 mM; p = 0.0198) in hippocampal neurons. Conclusion: long-term lithium treatment increases membrane phospholipid metabolism in neurons through the activation of total, c- and iPLA2. This effect is more prominent at sub-therapeutic concentrations of lithium, and the activation of distinct cytosolic PLA2 subtypes is tissue specific, i.e., iPLA2 in hippocampal neurons, and cPLA2 in cortical neurons. Because PLA2 activities are reported to be reduced in Alzheimer’s disease (AD) and bipolar disorder (BD), the present findings provide a possible mechanism by which long-term lithium treatment may be useful in the prevention of the disease.

Lithium Distinctly Modulates the Secretion of Pro- and Anti- Inflammatory Interleukins in Co-Cultures of Neurons and Glial Cells at Therapeutic and Sub-Therapeutic Concentrations.

Lithium is associated with various effects on immune functions, some of which are still poorly understood. The roles of many cytokines have been characterized in a variety of neurodevelopmental processes including neurogenesis, neuronal and glial cell migration, proliferation, differentiation, synaptic maturation and synaptic pruning. This work aims to evaluate the effects of different doses of lithium (0.02; 0.2 and 2mM) on the secretion of cytokines in co-cultures of cortical and hippocampal neurons with glial cells. Our results indicate that chronic treatment with lithium chloride at subtherapeutic concentrations are able to modify the secretion of pro- and anti-inflammatory interleukins in co-cultures of cortical and hippocampal neurons with glial cells.

The Absence of CYP3A5*3 Is a Protective Factor to Anticonvulsants Hypersensitivity Reactions: A Case-Control Study in Brazilian Subjects

Although aromatic anticonvulsants are usually well tolerated, they can cause cutaneous adverse drug reactions in up to 10% of patients. The clinical manifestations of the antiepileptics-induced hypersensitivity reactions (AHR) vary from mild skin rashes to severe cutaneous drug adverse reactions which are related to high mortality and significant morbidity. Genetic polymorphisms in cytochrome P450 genes are associated with altered enzymatic activity and may contribute to the risk of AHR. Here we present a case-control study in which we genotyped SNPs of CYP2C19, 2C9 and 3A5 of 55 individuals with varying severities of AHR, 83 tolerant, and 366 healthy control subjects from São Paulo, Brazil. Clinical characterization was based on standardized scoring systems and drug patch test. All in vivo investigation followed the ENDA (European Network of Drug Allergy) recommendations. Genotype was determined by real time PCR using peripheral blood DNA as a template. Of all 504 subjects, 65% were females, 45% self-identified as Afro-American, 38% as Caucasian and 17% as having non-African mixed ascendancy. Amongst 55 subjects with AHR, 44 had severe cutaneous drug adverse reactions. Of the 46 drug patch tests performed, 29 (63%) were positive. We found a strong association between the absence of CYP3A5*3 and tolerant subjects when compared to AHR (p = 0.0002, OR = 5.28 [CI95% 2.09–14.84]). None of our groups presented positive association with CYP2C19 and 2C9 polymorphisms, however, both SNPs contributed to separation of cases and tolerants in a Classification and Regression Tree. Our findings indicate that drug metabolism genes can contribute in the tolerability of antiepileptics. CYP3A5*3 is the most prevalent CYP3A5 allele associated with reduced enzymatic function. The current study provides evidence that normal CYP3A5 activity might be a protective factor to aromatic antiepileptics-induced hypersensitivity reactions in Brazilian subjects.

Association study in Alzheimer's disease of single nucleotide polymorphisms implicated with coffee consumption

Background There is evidence from animal and in vitro models of the protective effects of caffeine in Alzheimer’s disease. The suggested mechanisms through which caffeine may protect neurons against Alzheimer’s disease pathology include the facilitation of beta-amyloid clearance, upregulation of cholinergic transmission, and increased neuronal plasticity and survival. Epidemiological studies support that Alzheimer’s disease patients consume smaller amounts of coffee beverages throughout their lives as compared to age-matched cognitively healthy individuals. Objective The aim of the present study was to determine whether the negative association between Alzheimer’s disease and coffee consumption may be influenced by a common genetic predisposition, given the fact that the pattern of coffee consumption is determined by both environmental and genetic factors. Method We conducted an in silico search addressing the association between genetic polymorphisms related to coffee consumption and the diagnosis of Alzheimer’s disease. We further investigated the interactions between genes located in regions bearing these polymorphisms. Results Our analysis revealed no evidence for a genetic association (nor interaction between related proteins) involving coffee consumption and Alzheimer’s disease. Discussion The negative association between Alzheimer’s disease and coffee consumption suggested by epidemiological studies is most likely due to environmental factors that are not necessarily regulated by genetic background.

Regular multimodal aerobic exercise reduces pro-inflammatory cytokines and improves BDNF peripheral levels and executive functions in elderly MCI individuals with different BDNF Val66Met genotypes

*Statistical REDUCES PRO-INFLAMMATORY CYTOKINES AND IMPROVES BDNF PERIPHERAL LEVELS AND EXECUTIVE FUNCTIONS IN ELDERLY MCI INDIVIDUALS WITH DIFFERENT BDNF VAL66MET GENOTYPES Carla M.C. Nascimento, Marcia R. Cominetti, Jessica R. Pereira, Larissa P. Andrade, Marcelo Garuffi, Daniel S. Kerr, Orestes Vicente Forlenza, Florindo Stella, UFSCar Federal University of S~ao Carlos, Laboratory of Biology of Ageing (LABEN), S~ao Carlos, Brazil; UNESP Universidade Estadual Paulista, Biosciences Institute, Rio Claro, Brazil; Laboratory of Neurosciences, Institute of Psychiatry, Faculty of Medicine, University of S~ao Paulo, S~ao Paulo, Brazil; Laboratory of Neurosciences, Institute of Psychiatry, Faculty of Medicine, University of S~ao Paulo, S~ao Paulo, Brazil; UNESP Universidade Estadual Paulista, Biosciences Institute, Rio Claro, Brazil. Contact e-mail: carlamcnascimento@gmail.com

BDNF Val66Met polymorphism is not related with temporal lobe epilepsy caused by hippocampal sclerosis in Brazilian population

PURPOSE Some variants of the brain derived neurotrophic factors (BDNF) gene, namely the Val66Met (rs6265), may contribute the risk for epilepsy development. We aimed to investigate if this polymorphism was associated with the risk for epilepsy development in TLE-HS and its correlation with epilepsy-related factors and the presence of psychiatric disorders. METHODS We assessed 119 patients with unequivocal TLE-HS and 112 healthy controls. Individuals were genotyped for the polymorphisms of the gene encoding BDNF Val66Met. RESULTS There was no difference between TLE-HS and healthy controls, for the genotypic distribution (p = 0.636) and allelic distribution (p = 0.471). There was no correlation between Val66Met and epilepsy-related factors and for psychiatric comorbidities (p = 0.888). CONCLUSIONS Our findings demonstrated that polymorphism Val66Met is not associated with TLE-HS, epilepsy-related factors and psychiatric comorbidities in this selected group of patients.